Brown fuzzy algae

I'm struggling with this algae, which I'm having trouble even finding out what it is, let alone getting rid of it.


Brown fuzzy coating - tends to lower areas on some ?Lindernia, but I note similar on older leaves of some Hygrophila, and less so on Java Fern.


Tank set up for 6 months.


130L, temp 26-27 deg, GH 5.6


CO2 - pressurized, pH controller, pH drops from 7.72 in am to 6.60 through entire photoperiod, KH 3


Lights - LED, 2 strips of 12x3W (max power 1.5W each) - total period 10h, 2h sunrise/sunset, 6h 70% (plus 2hr @ 100%)


ferts - KNO3 to keep NO3 minimum 10ppm, KH2PO4 keep PO4 2-2.5ppm


water changes - 50% per week, add KHCO3 to boost KH to 3, add Seachem Equil to raise GH by 1.


micros - daily according to EI, use 'Amgrow chelated micronutrients' and approx 0.5mL Seachem Fe gluconate daily


(until this week I was doing 2x50% per week)


the pics show what I mean - the worst is on the lower zones of what I think is Lindernia (I think sold as pennywort). Some on older Hygrophila polysperma leaves, less so on Hygrophila leaves only 1-2weeks old.


I don't think this is diatoms - I had a major bloom of them at week 3-4 or so, which resolved, and this stuff doesn't come off like diatoms do.


I noted a thread elsewhere, where this stuff was thought to be a cyanobacteria. I am stumped.


Plants are growing rapidly, pearling nicely.


I'm starting to realise maybe I haven't been trimming properly, and the base of the pennywort is pretty old - probably 6 months.... I am planning to top it off, and probably bleach it....


Any thoughts??

 

hopefully pics will be visible now...


My wife works as a scientist in clinical microbiology - this brown matter under the microscope is rafts/chains of gram negative bacterial cells..... cyanobacteria.... should get a microscopy image later in the week, will post it when available.


To be honest I think it is already on the back foot - I added a circulation pump a week ago to blow more water into the corner where this stuff mostly is, it doesn't seem as thick now. I am planning on pulling this stuff up, and replanting the tops after probably giving them a good soak in something - I have the usual Excel/glut/H2O2/bleach, and can access any antibiotic - any suggestions?

 

From memory what happened was the diatom bloom came and went, then maybe in January/February, in the heat of summer, this got going - I tend to use the aircon if the tank temp is rising through 28.5 deg C (83 deg F) and the day is hot. Nutrients have always been pretty good, nitrates are never under 7.5ppm, generally 10-15ppm. The tank has an overhead trickle filter, and I've done minimum 50% water changes per week (twice weekly for the last 2 months). I had gotten pretty stingey with the micronutrients though, was down to under 1/3 or EI, and with two water changes..... I have picked this up now.


I'm not keen to treat the tank at this stage, may treat the plants in a bucket with erythromycin though, might double whammy them with H2O2 after!


Thanks for your reply Rob....

 

Cyano - top images above on Lindernia - Wet prep microscopy, no stains, just scraped and put under a cover-slip.




View attachment 10189

 

Microscopy of brown coating on Hygrophila - diatoms.....




View attachment 10190